This invention relates to an antimicrobial agent and its use together with an acid to provide a composition that possesses synergistic effects. More particularly, the invention provides a synergistic antimicrobial composition in the form of a quaternary ammonium compound and an acid such as boric, citric, and malic.
Antimicrobial agents are chemical compositions that are used to prevent microbiological contamination and deterioration of products, materials, and systems. Particular areas of application of antimicrobial agents and compositions are, for example, cosmetics, disinfectants, sanitizers, wood preservation, food, animal feed, cooling water, metalworking fluids, hospital and medical uses, plastics and resins, petroleum, pulp and paper, textiles, latex, adhesives, leather and hides, and paint slurries. Of the diverse categories of antimicrobial agents and compositions, quaternary ammonium compounds represent one of the largest of the classes of agents in use. At low concentrations, quaternary ammonium type antimicrobial agents are bacteriostatic, fungistatic, algistatic, sporostatic, and tuberculostatic. At medium concentrations they are bactericidal, fungicidal, algicidal, and viricidal against lipophilic viruses. Silicone containing quaternary ammonium compounds are well known as exemplified by U.S. Pat. No. 3,560,385, and the use of such compounds as antimicrobial agents is taught, for example, in a wide variety of patents such as U.S. Pat. Nos. 3,730,701, and 3,817,739, where the compounds are used to inhibit algae; 3,794,736 and 3,860,709 where they are employed for sterilizing or disinfecting a variety of surfaces and instruments; 3,865,728, where the compounds are used to treat aquarium filters; 4,259,103; and in British Patent No. 1,386,876. Published unexamined European Application No. 228464 of July 15, 1987, teaches that microorganisms on plants can be killed by the application thereto of an aqueous mixture of a surfactant and an organosilicon quaternary ammonium compound. In a particular application of an antimicrobial silicone quaternary ammonium compound, a paper substrate is rendered resistant to the growth of microorganisms in U.S. Pat. No. 4,282,366. In U.S. Pat. No. 4,504,541, an antimicrobial fabric is disclosed which is resistant to discoloration and yellowing by treatment of the fabric with a quaternary ammonium base containing an organosilicone. U.S. Pat. No. 4,516,937, as well as its companion U.S. Pat. No. 4,692,374, relate to wet wiper towelettes having an antimicrobial agent substantive to the fibers of the web and being an organosilicon quaternary ammonium compound. In a series of Burlington Industries, Inc. U.S. Pat. Nos. 4,408,996, 4,414,268, 4,425,372, and 4,395,454, such compounds are disclosed to be useful in surgical drapes, dressings, and bandages. This same assignee also disclose these compounds as being employed in surgeons' gowns in U.S. Pat. Nos. 4,411,928 and 4,467,013. Organosilicon quaternary ammonium compounds have been employed in carpets, in U.S. Pat. No. 4,371,577; applied to walls, added to paints, and sprayed into shoes, in U.S. Pat. No. 4,394,378; applied to polyethylene surfaces and used in pillow ticking in U.S. Pat. No. 4,721,511; in flexible polyurethane foams of fine-celled, soft, resilient articles of manufacture in U.S. Pat. No. 4,631,297; and mixed with a surfactant in Japanese Kokai Application No. 58-156809, filed Aug. 26, 1983, of Sanyo Chemical Industries, Ltd., for the purpose of achieving uniformity of distribution of compounds to a surface. Thus the versatility of such compositions is readily apparent. It is not new to employ an acid to kill germs. U.S. Pat. No. 4,034,079, is representative of the use of boric acid. In U.S. Pat. No. 4,084,747, lactic acid is utilized. What is new and not believed to be taught in the prior art is the concept of combining such acids with the particular silanes of the present invention to kill germs synergistically. In accordance with the present invention, it has been found that antimicrobial properties of silicone containing quaternary ammonium compounds can be improved by mixing the antimicrobial agent with an acid to produce a composition that acts synergistically in preventing microbiological contamination and deterioration of products, materials, and systems. For example, 3-(trimethoxysilyl)propyldimethyloctadecylammonium chloride is an effective antimicrobial agent in which the active ingredient hydrolyzes in water and reacts with substrates with which it is brought into contact. These substrates demonstrate nonleaching board spectrum antimicrobial activity. By including an acid component in the antimicrobial composition, such activity of this particular quaternary ammonium compound has been increased substantially against a mixed fungal culture where neither the acid nor the quaternary ammonium compound was effective alone. Hence, the compositions set forth in the present invention possess advantages over existing antimicrobial treating agents and provide improved results thereover, since the combinations disclosed herein of an antimicrobial agent together with an acid provide better results than when either of the individual components are employed separately. Thus, the disadvantages of the prior art are overcome with the present invention wherein improved antimicrobial agents are provided.